Question: I just moved into a house with a fireplace and- never having owned a fireplace before- I wanted to use it right away. It's the middle of winter and I've gotten conflicting opinions from my friends on how cold it should be outside to use your fireplace. A couple of friends said "Don't use it unless it's above 32 degrees outside." and a couple said "Use it whenever you want." Is there a certain at which it's most efficient to use my fireplace? Answer: The fireplace is inefficient at any temperature- but the colder it is-the more heat from your home (which you already paid to heat) will go up the chimney.So- use it anytime....but if you are going to use often you may consider upgrading it with a fireplace insert.